1. Field of the invention
The invention relates to a process for the simultaneous deposition of a protective coating, particularly an aluminium-based coating, on both the external and internal surfaces of heat-resistant alloy parts, particularly nickel-, cobalt- or iron-based alloy parts, and also relates to an apparatus for carrying out of the process.
2. Summary of the prior art
French Patent No. 1 433 497 describes a vapour-phase aluminization process whereby deposited aluminium is transferred without solid-solid contact between the donor containing the metal to be deposited and the part to be coated, the donor reacting with a halide, particularly a fluoride.
More recently, U.S. Pat. Nos. 4 132 816 and 4 148 275, for example, describe processes for obtaining improved protection of the internal surfaces of hollow parts, especially cooled turbine blades having fine and complex internal networks of passages. None of these known processes, however, is entirely satisfactory. In particular, the above U.S. Pat. Nos. 4 132 816 and 4 148 275 involve complicated operating procedures utilizing twin-compartment boxes and two separate donor sources when protection is to be achieved on both external and internal surfaces of parts.